Shows how to trigger an automatic unapproval when the account goes past due in Participants Database Member Payments

pdb-auto-unapprove.php

<?php
add_action( 'pdbmps-status_change_to_past_due', 'xnau_unapprove_record', 10, 2 );
function xnau_unapprove_record ( $status, $data )
{
  // this is so we can access a function in the plugin
  global $PDb_Member_Payments;
  // now set the record to not approved (2nd argument)
  $PDb_Member_Payments->approve_record( $data['id'], false );
}

This snippet would go in your theme functions file, or you could, by adding a WordPress plugin header, install it as a plugin.